Clinical observations indicate that alterations in many hormone systems affect intraocular pressure (IOP) and aqueous humor dynamics. However, laboratory data delineating their mechanisms of action are either lacking or inconsistent. This investigation incorporates the advanced technology in pituitary hormone modulators, cerebral perfusions, and radioimmunoassay to systematically explore the regulatory role of five endogenous pituitary hormones (corticotropin, gonadotropin, thyrotropin, prolactin, and growth hormone) and their modulators on aqueous humor dynamics. Various hormone modulators will be administered into conscious rabbits by pituitary microperfusion, ventriculocisternal perfusion, and intravenous perfusion. The alteration of relevant endogenous hormones will be determined by radioimmunoassay. The dose- response and time course of the IOP change will be documented. The original site of action will be determined by comparing the dose-response relations among the three types of perfusions. The hormonal, neural, and cardiovascular pathways mediating the IOP effect will be identified. The alterations in aqueous humor dynamics correlated with the hormonal effects will be determined using aqueous fluorophotometry. The involvement of intraocular sympathetic innervation, adenylate cyclase-cyclic AMP system in the ciliary processes, and intraocular autonomic neurotransmitters for each specific hormonal effect will be determined. This investigation will reveal the fundamental mechanisms of action of these pituitary hormone systems on aqueous humor dynamics. This new knowledge will broaden the basis for glaucoma research and refine our rationale in designing antiglaucoma medication.